Flags were dipped as a sign of recognition and respect, but I've never heard of it being done to a lighthouse.
Which reminds me of an old USN joke.
USN naval vessel calls up on an international frequency to object ahead in the mist:
For the first time: "This is USN XXX, please move out of the way"
A few minutes, for the second time: "This is USN XXX and we are heading towards you at speed. Move out of the way, NOW"
A further short time elapse, for the third time: "Move out of the way or I cannot answer for the consequences"
Object ahead, laconically: "This is a Canadian lighthouse. Your move"
Very much a "collapse of stout party" joke. Don't tell me it isn't true.